The present invention relates generally to photoimageable compositions. In particular, the present invention relates to photoimageable silsesquioxane compositions.
Photoresists are photosensitive films used for transfer of images to a substrate. A coating layer of a photoresist is formed on a substrate and the photoresist layer is then exposed through a photomask to a source of activating radiation. The photomask has areas that are opaque to activating radiation and other areas that are transparent to activating radiation. Exposure to activating radiation provides a photoinduced chemical transformation of the photoresist coating to thereby transfer the pattern of the photomask to the photoresist-coated substrate. Following exposure, the photoresist is developed to provide a relief image that permits selective processing of a substrate.
A photoresist can be either positive-acting or negative-acting. For most negative-acting photoresists, those coating layer portions that are exposed to activating radiation polymerize or crosslink in a reaction between a photoactive compound and polymerizable agents of the photoresist composition. Consequently, the exposed coating portions are rendered less soluble in a developer solution than unexposed portions. For positive-acting photoresists, exposed portions are rendered more soluble in a developer solution while areas not exposed remain comparatively less developer soluble. In general, photoresist compositions include at least a resin binder component and a photoactive agent.
More recently, chemically-amplified type resists have been increasingly employed, particularly for formation of sub-micron images and other high performance applications. Such photoresists may be negative-acting or positive-acting and generally include many crosslinking events (in the case of a negative-acting resist) or deprotection reactions (in the case of a positive-acting resist) per unit of photogenerated acid. In the case of positive chemically-amplified resists, certain cationic photoinitiators have been used to induce cleavage of certain xe2x80x9cblockingxe2x80x9d groups pendant from a photoresist binder, or cleavage of certain groups comprising a photoresist binder backbone. See, for example, U.S. Pat. Nos. 5,075,199; 4,968,581; 4,810,613; and 4,491,628 and Canadian Patent Application 2,001,384. Upon cleavage of the blocking group through exposure of a coating layer of such a resist, a polar functional group is formed, e.g. carboxyl or imide, which results in different solubility characteristics in exposed and unexposed areas of the resist coating layer. See also R. D. Allen et al. Proceedings of SPIE, 2724:334-343 (1996); and P. Trefonas et al. Proceedings of the 11th International Conference on Photopolymers (Soc. of Plastics Engineers), pp 44-58 (Oct. 6, 1997).
The increasing density of integrated circuits has created a need for higher resolution patterning capabilities. One method of improving resolution involves using a shorter wavelength light during pattern formation. Shorter wavelengths of approximately 200 to 280 nm may be obtained by using a deep UV (xe2x80x9cDUVxe2x80x9d) source such as a mercury/xenon (xe2x80x9cHg/Xexe2x80x9d) lamp with appropriate filters. Additionally, KrF (248 nm) or ArF (193 nm) excimer lasers may be used as exposure sources. However, at shorter wavelengths the depth of focus of the exposure tool, which may be an excimer stepper, or step and scan tool, may be adversely affected. The depth of focus (xe2x80x9cDOFxe2x80x9d) is an expression of the range of distances from the image focal plane through which the projected image remains in subjectively acceptable focus. DOF is related to wavelength and lens numerical aperture according to the formula: DOF xcex1xcex/2(NA)2 where xcex is the wavelength of exposing light and NA is the numerical aperture of the lens. Generally, a depth of focus of 1 to 2 xcexcm is required for an adequate lithographic process window, in order to accommodate variations in the thickness or height of the resist film.
In addition to using shorter wavelengths during exposure, it is also desirable to use a thinner layer of resist. However, the major drawback of using a thin layer of resist is that the variation of resist thickness over a diffusion step on a substrate and into an etched pattern increases as the pattern size becomes smaller. This variation means that the dimensions of any pattern being imaged in the resist will vary as the step geometry is traversed. Therefore, in a single layer resist system, the lack of dimensional control on the wafer can create different line widths throughout the resist which reduces the quality of the electronic package.
To improve dimensional control, bilayer (or bilevel or multilevel) resist systems are often utilized. In a typical bilevel system, a bottom resist is first applied to a substrate to planarize wafer topography. The bottom resist is cured and a second thinner imaging top resist is then applied over the bottom resist. The top resist is then soft baked, and patterned (or imaged) using conventional resist exposure and development, followed by etch transfer of the top pattern through the bottom resist using the top resist pattern as an etch mask. Positive resists are commonly used in bilayer applications and are typically based on novolac resins, which are condensation polymers of phenols or substituted phenols and formaldehyde.
Sugiyama et al., Positive Excimer Laser Resists Prepared with Aliphatic Diazoketones, Soc. Plastics Eng., Conference Proceedings, pages 51-60 (November 1988), disclose a new class of alkali-developable positive excimer laser resists designed for DUV lithography. Such resists are two-component resists and contain xcex1-diazoacetoacetates blended with polyhydroxybenzylsilsesquioxane as a matrix resin.
U.S. Pat. No. 4,745,169 (Sugiyama et al.) discloses silicon-containing polymers for use in bilayer resist applications. The base soluble silsesquioxane polymer is synthesized by reacting trimethylsilyl iodide with polymethoxybenzyl-silsesquioxane to form aryl-O-trimethyl silyl groups. These trimethyl silyl groups are then hydrolyzed in water to form hydroxy groups. However, this reaction is not highly reproducible and often gives crosslinked polymer. Moreover, when these polymers are combined with diazonaphthoquinone-based photoactive compounds, exposure doses of  greater than 100 mJ/cm2 at 365 nm are required to pattern the resist. Resists containing such photoactive compounds are too optically dense in the 200 to 280 nm region to be practical for DUV lithography. The optical density is greater than 0.5 for a 0.3 xcexcm film of 20% photoactive compound in any polymer and the imaging dose is greater than 50 mJ/cm2 in the DUV range. The optical density should be less than 0.3 or 0.4 xcexcm for a single layer resist film in order to provide the most vertical wall profiles. For thinner films in a bilayer system the optical density should typically be less than or equal to 0.3 for a 0.3 to 0.4 xcexcm film.
U.S. Pat. No. 5,338,818 (Brunsvold et al.) discloses certain acid sensitive polymers suitable for use in bilayer resist systems. Such polymers are copolymers of hydroxyphenyl- or hydroxybenzyl-silsesquioxane/RO-phenyl- or RO-benzyl-silsesquioxane, where R is selected from certain acid sensitive groups.
Conventional silicon-containing polymers, such as the above discussed silsesquioxane polymers, for use in bilayer resist systems have dissolution rates that are too high. Such high dissolution rates can negatively affect the lithographic performance of such bilayer resist systems. Such dissolution rate may be controlled by increasing the amount of blocking (or acid cleavable) groups in a positive photoresist system. However, such increased amount of blocking results in slower photospeeds and a reduced percentage of silicon in the resist. Such reduced silicon content may adversely affect the etch resistance of the resist.
There is thus a need for polymers suitable for use in bilayer resists that have controlled and/or lower dissolution rates than conventional bilayer resist polymers, with little or no loss of photospeed.
It has been surprisingly found that the present silsesquioxane-containing polymers are suitable for use in bilayer resist systems and have lower dissolution rates than conventional silsesquioxane polymers. It has been further found that the present polymers have improved lithographic performance as compared to such conventional bilayer silsesquioxane polymers.
In a first preferred aspect of the invention, a silicon copolymer is provided that comprises phenyl groups and includes at least the following three repeating units 1) units that contain photoacid-labile groups; 2) units that are free of photoacid-labile and aqueous developing groups; and 3) units that contribute to the aqueous, alkaline developability of a photoresist containing the polymer. Such polymers are particularly useful in chemically-amplified positive acting photoresists (resist has acid-labile groups undergo a cleavage or deblocking reaction in the presence of photoacid during lithographic processing).
In such copolymers, preferred photoacid-labile groups include photoacid-labile esters or acetal groups, such as may be grafted onto phenolic xe2x80x94OH groups. For instance, an ester grafted onto a hydroxy group is a preferred acid-labile group (de-esterification occurs in the presence of photogenerated acid to provide developer-solublizing carboxy group). Such esters may be provided e.g. by reaction of a haloacetate compound (e.g. tert-butyl chloroacetate) with a phenolic hydroxy group. Acetal groups also are preferred photoacid-labile groups; for example a vinyl ether compound may be grafted onto a phenolic hydroxy moiety to provide a photoacid-labile acetal group. Suitable vinyl ether reagents to provide a photoacid-labile acetal group include compounds having at least one xe2x80x94(CHxe2x95x90CH)xe2x80x94Oxe2x80x94 group such as ethylvinyl ether and the like.
Preferred repeat units that can contribute to aqueous developability of a photoresist containing the polymer include hydroxy, carboxy and other polar preferably acidic groups such as sulfonic acid and the like. For instance, a preferred repeat unit of this type is a phenolic unit, or other hydroxy-containing unit.
In such copolymers, units that are free of photoacid-labile and aqueous, alkaline developing groups will be free of moieties as discussed above, i.e. photoacid-labile ester or acetal moieties, or hydroxy, carboxy or sulfonic acid moieties. Preferred repeat units of this type include phenyl or alkyl groups that are not substituted with such photoacid-labile or aqueous, alkaline developing moieties, e.g. alkyl or phenyl groups that are either unsubstituted or substituted by one or more halo, unsubstituted alkyl, non-photoacid labile alkoxy, mesyl groups or other sulfonic esters such as those of the formula C1-8alkylSO3xe2x80x94 and the like.
In such polymers, phenyl groups are preferably pendant to a polymer backbone that comprises linked Si groups or more preferably linked SiO groups.
A particularly preferred copolymer for use in photoimageable compositions of the invention includes Si atoms, with repeat units comprising i) phenol, ii) phenyl groups that comprise photoacid-labile moieties, and iii) phenyl groups that are either unsubstituted or substituted by groups that are other than photoacid-labile groups or aqueous, alkaline developing groups, such as sulfonyl acid esters, halogen, alkyl, etc. Preferably, with such polymers, the phenyl groups of units i), ii) and iii) are pendant groups and the polymer backbone comprises linked Si or SiO groups.
In a further aspect of the invention, photoimageable compositions are provided that include a polymer component and a photoactive component, wherein the component comprises a resin that includes as polymerized units one or more monomers of formula I and one or more monomers of formula II
(R1SiO3/2)xe2x80x83xe2x80x83(I)

wherein R1 is selected from (C1-C12)alkyl, substituted (C1-C12)alkyl, (C2-C6)alkenyl, substituted (C2-C6)alkenyl, phenyl, C6(R7)5, (C1-C5)alkyl(C6(R7)4), (C1-C5)alkyl(C6H4OZ), vinyl and substituted vinyl; Z is selected from (C1-C6)alkylsulfonate ester or arylsulfonate ester; each R7 is independently selected from H, F, (C1-C6)alkyl, (C1-C6)alkoxy, halo(C1-C6)alkyl, hydroxy-halo(C1-C6)alkyl or halo(C1-C6)alkoxy; each R4 is independently selected from R7 and OH; each R5 is independently selected from H or F; each R6 is independently selected from H, F, CH3, CF3, CHF2, and CH2F; and m=0-2.
In another aspect, the present invention provides a method of forming a relief image including the steps of depositing a photoimageable composition on a substrate and imaging the photoimageable composition through a mask to provide a relief image, wherein the photoimageable composition includes a binder polymer and a photoactive component, wherein the binder polymer includes as polymerized units one or more monomers of formula I and one or more monomers of formula II
(R1SiO3/2)xe2x80x83xe2x80x83(I)

wherein R1 is selected from (C1-C12)alkyl, substituted (C1-C12)alkyl, (C2-C6)alkenyl, substituted (C2-C6)alkenyl, phenyl, C6(R7)5, (C1-C5)alkyl(C6(R7)4), (C1-C5)alkyl(C6H4OZ), vinyl and substituted vinyl; Z is selected from (C1-C6)alkylsulfonate ester or arylsulfonate ester; each R7 is independently selected from H, F, (C1-C6)alkyl, (C1-C6)alkoxy, halo(C1-C6)alkyl, hydroxy-halo(C1-C6)alkyl or halo(C1-C6)alkoxy; each R4 is independently selected from R7 and OH; each R5 is independently selected from H or F; each R6 is independently selected from H, F, CH3, CF3, CHF2, and CH2F; and m=0-2.
In a further aspect, the present invention provides a method of manufacturing an electronic device including the steps of disposing on an electronic device substrate a photoimageable composition including a binder polymer and a photoactive component, wherein the binder polymer includes as polymerized units one or more monomers of formula I and one or more monomers of formula II
(R1SiO3/2)xe2x80x83xe2x80x83(I)

wherein R1 is selected from (C1-C12)alkyl, substituted (C1-C12)alkyl, (C2-C6)alkenyl, substituted (C2-C6)alkenyl, phenyl, C6(R7)5, (C1-C5)alkyl(C6(R7)4), (C1-C5)alkyl(C6H4OZ), vinyl and substituted vinyl; Z is selected from (C1-C6)alkylsulfonate ester or arylsulfonate ester; each R7 is independently selected from H, F, (C1-C6)alkyl, (C1-C6)alkoxy, halo(C1-C6)alkyl, hydroxy-halo(C1-C6)alkyl or halo(C1-C6)alkoxy; each R4 is independently selected from R7 and OH; each R5 is independently selected from H or F; each R6 is independently selected from H, F, CH3, CF3, CHF2, and CH2F; and m=0-2; imaging the photoimageable composition through a mask; and developing the photoimageable composition.
In yet a further aspect, the present invention provides a photoimageable composition including a binder polymer and a photoactive component, wherein the binder polymer includes as polymerized units one or more monomers of formula I, one or more monomers of formula II and one or more monomers of formula III
(R1SiO3/2)xe2x80x83xe2x80x83(I)

wherein R1 is selected from (C1-C12)alkyl, substituted (C1-C12)alkyl, (C2-C6)alkenyl, substituted (C2-C6)alkenyl, phenyl, C6(R7)5, (C1-C5)alkyl(C6(R7)4), (C1-C5)alkyl(C6H4OZ), vinyl and substituted vinyl; Z is selected from (C1-C6)alkylsulfonate ester or arylsulfonate ester; R2 is an acid cleavable group; each R7 and R8 is independently selected from H, F, (C1-C6)alkyl, (C1-C6)alkoxy, halo(C1-C6)alkyl, hydroxy-halo(C1-C6)alkyl or halo(C1-C6)alkoxy; each R4 is independently selected from R7 and OH; each R5 and R9 is independently selected from H or F; each R6 and R10 is independently selected from H, F, CH3, CF3, CHF2, and CH2F; m=0-2; and p=0-2.
In yet another aspect, the present invention provides a method of forming a relief image including the steps of depositing a photoimageable composition on a substrate and imaging the photoimageable composition through a mask to provide a relief image, wherein the photoimageable composition includes a binder polymer and a photoactive component, wherein the binder polymer includes as polymerized units one or more monomers of formula I, one or more monomers of formula II and one or more monomers of formula III
(R1SiO3/2)xe2x80x83xe2x80x83(I)

wherein R1 is selected from (C1-C12)alkyl, substituted (C1-C12)alkyl, (C2-C6)alkenyl, substituted (C2-C6)alkenyl, phenyl, C6(R7)5, (C1-C5)alkyl(C6(R7)4), (C1-C5)alkyl(C6H4OZ), vinyl and substituted vinyl; Z is selected from (C1-C6)alkylsulfonate ester or arylsulfonate ester; R2 is an acid cleavable group; each R7 and R8 is independently selected from H, F, (C1-C6)alkyl, (C1-C6)alkoxy, halo(C1-C6)alkyl, hydroxy-halo(C1-C6)alkyl or halo(C1-C6)alkoxy; each R4 is independently selected from R7 and OH; each R5 and R9 is independently selected from H or F; each R6 and R10 is independently selected from H, F, CH3, CF3, CHF2, and CH2F; m=0-2; and p=0-2.
In still another aspect, the present invention provides a method of manufacturing an electronic device including the steps of disposing on an electronic device substrate a photoimageable composition including a binder polymer and a photoactive component, wherein the binder polymer includes as polymerized units one or more monomers of formula I, one or more monomers of formula II and one or more monomers of formula III
(R1SiO3/2)xe2x80x83xe2x80x83(I)

wherein R1 is selected from (C1-C12)alkyl, substituted (C1-C12)alkyl, (C2-C6)alkenyl, substituted (C2-C6)alkenyl, phenyl, C6(R7)5, (C1-C5)alkyl(C6(R7)4), (C1-C5)alkyl(C6H4OZ), vinyl and substituted vinyl; Z is selected from (C1-C6)alkysulfonate ester or arylsulfonate ester; R2 is an acid cleavable group; each R7 and R8 is independently selected from H, F, (C1-C6)alkyl, (C1-C6)alkoxy, halo(C1-C6)alkyl, hydroxy-halo(C1-C6)alkyl or halo(C1-C6)alkoxy; each R4 is independently selected from R7 and OH; each R5 and R9 is independently selected from H or F; each R6 and R10 is independently selected from H, F, CH3, CF3, CHF2, and CH2F; m=0-2; and p=0-2; imaging the photoimageable composition through a mask; and developing the photoimageable composition.
In a still further aspect, the present invention provides a polymer including as polymerized units one or more monomers of formula I and one or more monomers of formula II
(R1SiO3/2)xe2x80x83xe2x80x83(I)

wherein R1 is selected from (C1-C12)alkyl, substituted (C1-C12)alkyl, (C2-C6)alkenyl, substituted (C2-C6)alkenyl, phenyl, C6(R7)5, (C1-C5)alkyl(C6(R7)4), (C1-C5)alkyl(C6H4OZ), vinyl and substituted vinyl; Z is selected from C1-C6)alkyl, ester or arylsulfonate ester; each R7 is independently selected from H, F, (C1-C6)alkyl, (C1-C6)alkoxy, halo(C1-C6)alkyl, hydroxy-halo(C1-C6)alkyl or halo(C1-C6)alkoxy; each R4 is independently selected from R7 and OH; each R5 is independently selected from H or F; each R6 is independently selected from H, F, CH3, CF3, CHF2, and CH2F; and m=0-2.
In an even further embodiment, the present invention provides an optical waveguide having a core and a cladding, wherein at least one of the core and cladding includes as polymerized units the polymer described above.